Detection of circulating T cells with CD4(+)CD7(-) immunophenotype in patients with benign and malignant lymphoproliferative dermatoses

Background: Cutaneous T-cell lymphomas (CTCLs) are malignancies of CD4(+) T cells that involve the skin. CD4(+)CD7(-) cells may represent a malignant population in CTCL. Objective: Our purpose was to compare the percentage of CD4(+)CD7(-) cells and the expression of pan-TT-cell antigens in blood lymphocytes from 31 patients with benign dermatoses with 35 patients who had CTCL. Methods: The patients with CTCL were classified as follows: 10 with mycosis fungoides (MF), seven with pre-Sezary syndrome (pre-SS), and 18 with Sezary syndrome (SS). Flow cytometry was used to determine the percentage of CD4(+)CD7(-) cells and the CD4/CD8 ratio and to detect aberrant expression of the pan-T-cell antigens CD2, CD3, and CD5. Results: We found a mean of 5.8% CD4(+)CD7(-) cells for the 16 normal control subjects and 9.3% for the benign cases (p = 0.13). The patients with pre-SS and SS had a higher percentage of CD4(+)CD7(-) cells (22.4% and 35.5%, respectively) than patients with beni,on dermatoses (p < 0.01); no difference was found between patients with benign dermatoses and those with MF (p = 0.80). The mean CD4/CD8 ratio was 3.1 for the normal control subjects compared with 7.4 for the patients with benign dermatoses (p < 0.01). Patients with SS had a ratio of 49, which was higher than the ratio for those with benign dermatoses (p < 0.01); however, the ratio for patients with MF and pre-SS did not differ from that of the group with benign dermatoses (p = 0.71 and 0.55, respectively). Aberrant CD2, CD3, or CD5 expression was observed in 66% of patients with SS, 29% with pre-SS, 30% with MF, but in none of the patients with a benign dermatosis. Conclusion: Small numbers of CD4(+)CD7(-) cells can be found by flow cytometry in patients with a benign dermatosis and in normal control subjects. This T-cell subset is expanded in pre-SS and SS but not in MF. Aberrant pan-T-cell antigen expression is commonly observed in patients with SS but not in patients with a benign dermatosis.